The present invention generally relates to a magnetoresistance effect type head and a manufacturing method therefor and, more particularly, to a technique which can be effectively used for a magnetic head of a magnetic disc device or the like.
A magnetoresistive head is a reproduction exclusive head utilizing such a phenomenon that the electric resistance of a magnetoresistance effect type film, which will be sometimes referred to merely as the MR film, hereinafter, varies depending on its magnetizing direction.
The magnetoresistive head comprises lower and upper magnetic shield films made of magnetic material and an MR element disposed between the upper and lower magnetic shield films. The MR element has an MR film, bias films for applying a horizontal bias to the MR film, and a pair of conductive electrodes for passing a signal detection signal to the MR film. A magnetic domain control layer may be provided in the MR element to provide a single magnetic domain to the MR film. A current is continuously passed to the MR film through the conductive electrodes, and a voltage between the electrodes is continuously detected. When a leak magnetic field ranging from a magnetic recording medium to the MR film varies, this causes the magnetizing direction of the MR film to be varied so that the resistance of the MR film is changed and a signal is generated between the electrodes. In this manner, information is reproduced from the medium.
The processes for forming the electrodes and MR film of the prior art MR element include (a) formation of the MR film on the electrodes and (b) formation of the electrodes on the MR film.
The process (a) has a problem that the formation of the MR film on the electrodes involves the formation of steps in the MR film and the formation of magnetic walls in the steps, which results in generation of Barkhausen noise at the time of reproduction.
The process (b) can avoid such a problem as the formation of the steps in the MR film unlike the process (a), but process (b) is defective in that the formation of the electrodes on the MR film causes damage of the MR film. More specifically, when an electrode film is formed on the MR film and then subjected to an ion milling for formation of the electrodes for example, the MR film is damaged because of its subjection to ions.
For the purpose of minimizing the damage of the MR film, there has been suggested an electrode processing method which is based on a reactive ion etching. In this method, as shown in JP-A-Hei 4-3306, a film Nb, Ta, Ti or the like capable of being subjected to a dry etching with use of such a fluorocarbon gas as a CF.sub.4 gas for formation of electrodes, or a film of Au, Pt, Cr or the like capable of being subjected to an etching with use of a chlorine-series gas, is formed on an MR or bias film subjected to a patterning of a predetermined shape, and subsequently the etched film is subjected to an etching to form electrodes having a desired shape. During the over-etching for the formation of the electrodes with use of the fluorocarbon gas or chlorine-series gas, the MR or bias film is subjected to the etching and therefore damaged.
Disclosed in JP-A-63-117309 (U.S. Pat. No. 4,713,708) is a magnetoresistance effect type head reader/converter in which a spacer film and a soft magnetic thin film are provided on an MR film. This invention also discloses vertical/horizontal biasing effects based on the use of a vertical bias film and a soft bias film.